In their unboxed form value types do not inherit from any type. Boxed value types shall inherit directly from System.ValueType unless they are enumerations, in which case, they shall inherit from System.Enum. Boxed value types shall be sealed.
Logically, the boxed type corresponding to a value type
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Is an object type.
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Will specify which object type is its base type (i.e., the object type from which it inherits).
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Will have a base type that has no fields defined.
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Will be sealed to avoid dealing with the complications of value slicing.
The more restrictive rules specified here allow for more efficient implementation without severely compromising functionality.